Patent Application
20240019272
The present disclosure relates to a linear actuator, magnetic sensor system and method of use. In particular, the present disclosure relates to a magnetic sensor system and method of use for monitoring the position a component driven by a rotatable mechanism in a linear direction.
Magnetic sensor systems comprising single turn angle sensors and multi-turn sensors are commonly used in applications where there is a need to monitor both the number of times a device has been turned and its precise angular position. An example is a steering wheel in a vehicle. Magnetic multi-turn sensors typically include magnetoresistive elements that are sensitive to an applied external magnetic field. The resistance of the magnetoresistive elements can be changed by rotating a magnetic field within the vicinity of the sensor. Variations in the resistance of the magnetoresistive elements will be tracked to determine the number of turns in the magnetic fields, which can be translated to a number of turns in the device being monitored. Similarly, magnetic single turn sensors measure the magnetic field angle of the rotating magnetic field, which can be translated to an angular position of the device being monitored.
The present disclosure provides a linear actuator apparatus, magnetic sensor system and method of use for detecting a position of a component driven by a rotatable mechanism in a linear direction. A magnetic sensing device comprising both a multi-turn (MT) sensor and a single turn (ST) sensor is provided within the same semiconductor package and placed in the vicinity of the rotatable mechanism. A magnet is mounted on the rotatable mechanism, such that, as the mechanism rotates, a rotating magnetic field is generated. The MT sensor measures the number of turns of the rotating magnetic field, which is translated to the number of turns of the rotatable mechanism. The ST sensor measures the angle of the rotating magnetic field, which is translated to an angular position of the rotatable mechanism. As each turn of the rotatable mechanism will be translated to a specific amount of linear motion, the amount by which the rotational mechanism has turned is proportional to the distance travelled by the driven component, and thus indicative of the linear position. Therefore, by placing a magnet and the magnetic sensing device in relation to the rotatable mechanism, with the multi-turn sensor providing the number of turns and the angle sensor providing the precise angular position within each turn, the measured rotational position can be translated to a corresponding linear position of the element being moved linearly as a result of the rotation.
Such an arrangement provides a compact and robust device for measuring linear position, which removes the need for installing a linear position system on the linearly driven component.
A first aspect of the present disclosure provides a linear actuator apparatus, comprising:
The angle sensor and the multi-turn sensor are preferably arranged on a first integrated circuit board. That is to say, the multi-turn sensor and angle sensor are provided in the same magnetic sensor package, which can be easily installed in proximity to the magnet without taking up a significant amount of space.
The at least one magnetic sensing device may further comprise processing means for determining the position of the first component in the linear direction.
The angle sensor is preferably configured to detect the orientation of the magnetic field over a range of 0° to 180°. That is to say, the angle sensor will determine the absolute angle position within each half turn.
The angle sensor may be one of: an anisotropic magnetoresistive (AMR) based single turn sensor, a giant magnetoresistive (GMR) based single turn sensor, a tunnel magnetoresistive (TMR) based single turn sensor, a Hall effect sensor and an inductive sensor.
The multi-turn sensor may be a giant magnetoresistive (GMR) based multi-turn sensor, or a tunnel magnetoresistive (TMR) based multi-turn sensor.
The multi-turn sensor may comprise a plurality of magnetoresistive elements electrically connected in series and physically laid out in a spiral configuration.
In such cases, the multi-turn sensor may further comprise a matrix of electrical connections arranged to electrically connect magnetoresistive elements of the plurality of magnetoresistive elements to other magnetoresistive elements of the plurality of magnetoresistive elements, the matrix being at least three by three.
The rotatable mechanism may comprise a first cylindrical gear, and wherein the first component comprises a linear gear configured to cooperate with the first cylindrical gear, such that rotation of the first cylindrical gear causes the linear gear to translate in a linear direction. For example, each gear may comprise teeth that cooperate together, to thereby provide a rack and pinion arrangement.
The rotatable mechanism may further comprise a second cylindrical gear configured to cooperate with the first cylindrical gear, such that rotation of the second cylindrical gear causes a corresponding rotation of the first cylindrical gear.
In such cases, the magnet may be mounted in relation to the first cylindrical gear or the second cylindrical gear. As such, the magnet will rotate with one of the gears, thereby generating a rotating magnetic field, the magnetic sensing device therefore monitoring the rotation of whichever gear the magnet is mounted on.
The rotatable mechanism may comprise a threaded screw and a cylindrical gear, wherein the threaded screw is configured to cooperate with the cylindrical gear such that rotation of the threaded screw causes a rotation of the cylindrical gear. For example, the rotatable mechanism may be a worm drive arrangement comprising a worm and worm gear.
In such arrangements, the first component may then comprise a linear gear configured to cooperate with the cylindrical gear, such that rotation of the cylindrical gear causes the linear gear to translate in a linear direction.
In other arrangements, the rotatable mechanism may comprise a threaded shaft, wherein the first component comprises an annular part arranged around the threaded shaft and configured to engage with the threaded shaft such that rotation of the threaded shaft causes the annular part to translate in a linear direction along the threaded shaft. An example of such an arrangement is a leadscrew with a nut that moves along the leadscrew as it rotates.
In some cases, the threaded shaft may further comprise a gear arrangement configured to drive the rotation of the threaded shaft. In such cases, the magnet may be mounted on the gear arrangement.
The magnet may be a single pole pair magnet or a multi-pole magnet.
In cases where the magnet is a multi-pole ring magnet, the at least one magnetic sensing device may be located in a first position adjacent to an outer circumferential edge of the multi-pole magnet, and/or a second position in front of the multi-pole magnet aligned with a pole pair.
The linear actuator apparatus may further comprise a motor configured to drive the rotatable mechanism.
The linear actuator apparatus may further comprise an electromagnet for initialising the angle sensor and multi-turn sensor.
The linear actuator apparatus may further comprise a protective shield formed around the magnet and magnetic sensing device. For example, the protective shield may comprise a ferromagnetic material. This shields the sensing device from stray magnetic fields that could cause a false reading.
The linear actuator apparatus may further comprise a linear sensor system. For example, the linear sensor system may comprise an incremental linear track comprising a first number of magnetic poles, and a further magnetic sensing device configured to count the first number of magnetic poles.
A second aspect of the present disclosure provides a method of monitoring position using a magnetic sensing device, wherein a magnet is mounted on a rotatable mechanism configured to actuate a first component in a linear direction, the method comprising:
Determining the position of the first component in the linear direction may comprise determining an amount of rotation by the rotatable mechanism in a first direction, and determining a distance travelled by the first component in the linear direction based on the determined amount of rotation. In this respect, the amount of rotation by the rotatable mechanism is proportional to the distance travelled by the first component, and thus the measured rotation can be directly translated to a linear position.
The angle sensor and the multi-turn sensor are preferably arranged on a first integrated circuit board.
Detecting the orientation of the magnetic field preferably comprises detecting the orientation of the magnetic field over a range of 0° to 180°.
The method may further comprise initialising the angle sensor and/or multi-turn sensor when the first component is at a starting position.
A further aspect of the present disclosure provides a computer system comprising:
A further aspect of the present disclosure provides a magnetic sensor system for monitoring position, comprising:
The angle sensor and the multi-turn sensor are preferably arranged on a first integrated circuit board.
The at least one magnetic sensing device may further comprise processing means for determining the position of the first component in the linear direction.
The angle sensor is preferably configured to detect the orientation of the magnetic field over a range of 0° to 180°.
The present disclosure will now be described by way of example only with reference to the accompanying drawings in which:
Magnetic multi-turn and single turn sensors can be used to monitor the turn count and angular position of a rotating shaft. Such magnetic sensing can be applied to a variety of different applications, such as automotive applications, medical applications, industrial control applications, consumer applications, and a host of other applications which require information regarding a position of a rotating component.
The present disclosure provides a linear actuator apparatus, magnetic sensor system and method of use for detecting a position of a component driven by a rotatable mechanism in a linear direction, for example, a rack and pinion arrangement or a nut on a leadscrew. A magnetic sensing device comprising both a multi-turn (MT) sensor and a single turn (ST) sensor is provided within the same semiconductor package and placed in the vicinity of the rotatable mechanism. A magnet is also mounted on the rotatable mechanism, such that, as the mechanism rotates, a rotating magnetic field is generated. The MT sensor measures the number of turns of the rotating magnetic field, which is translated to the number of turns of the rotatable mechanism. The ST sensor measures the angle of the rotating magnetic field, which is translated to an angular position of the rotatable mechanism. As each turn of the rotatable mechanism will be translated to a specific amount of linear motion, the amount by which the rotational mechanism has turned is proportional to the distance travelled, and thus indicative of the linear position. Therefore, by placing a magnet and the magnetic sensing device in relation to the rotatable mechanism, with the multi-turn sensor providing the number of turns and the angle sensor providing the precise angular position within each turn, the measured rotational position can be translated to a corresponding linear position of the element being moved linearly as a result of the rotation.
Such an arrangement provides a compact and robust device for measuring linear positions, which removes the need for installing a linear position system on the linearly driven component.
The sensing device 1 also comprises a processing circuit 106, and an integrated circuit 100 on which the MT sensor 102, the ST sensor 104 and processing circuit 106 are disposed. The processing circuit 106 receives signals SMT 112 from the MT sensor 102 and processes the received signals to determine that the turn count using a turn count decoder 108, which will output a turn count representative of the number of turns of an external magnetic field (not shown) rotating in the vicinity of the MT sensor 102, for example, a magnetic field generated by a magnet mounted on a rotatable mechanism that is driving another element in a linear direction. Similarly, the processing circuit 106 may also receive signals SST 114 from the ST sensor 104 and process the received signals using an angle decoder 110 to output an angular position of the external magnetic field. As will be described in more detail below, the turn count and angular position may then be input to a position decoder 116 that is configured to calculate the linear position of the driven element based on the amount the rotatable mechanism that rotated.
In
In order to measure the varying resistance of the magnetoresistive elements 204 as domain walls are generated, the magnetic strip 202 is electrically connected to a supply voltage VDD 208 and to ground GND 210 to apply a voltage between a pair of opposite corners. The corners halfway between the voltage supplies are provided with electrical connections 212 so as to provide half bridge outputs. As such, the multi-turn sensor 2 comprises multiple Wheatstone bridge circuits, with each half bridge 212 corresponding to one half turn or 180 degree rotation of an external magnetic field. Measurements of voltage at the electrical connections 212 can thus be used to measure changes in the resistance of the magnetoresistive elements 204, which can thus be used to determine the number of turns in the magnetic field, for example, by outputting the voltage measurements to the turn count decoder 108.
The example shown in
As an alternative, the MT sensor 102 may be a closed-loop spiral, wherein the magnetoresistive elements of the inner and outer spiral winding are connected together to form a continuous spiral. Such an arrangement provides the effect of numerous spirals connected together, which enables a very high number of turns to be counted.
A single pole pair magnet 306 is mounted on the end of the rotating shaft 304 such that a rotating magnetic field is produced. A magnetic sensing device 308, which may be the magnetic sensing device 1 described with reference to
As described previously, the rack 302 is moved linearly as the gear 300 rotates in one direction or the other. The magnetic sensing device 308 measures the rotating magnetic field generated by the magnet 306 to measure the amount by which the gear 300 has rotated in either direction, by counting the number of turns made and the absolute angular position within each turn, or preferably, within each half turn, which is then used to determine the linear position of the toothed rack 302. For example, the gear 300 may be turned 3 full turns in a clockwise direction, as measured by the MT sensor 102, and a further 45°, as measured by the ST sensor 104. Based on these measurements and the proportional relationship between the respective movements of the gear 300 and the rack 302, which may, for example, be based on the size and number of cooperating teeth, the distance travelled by the rack 302 and thus its linear position can be determined, for example, by the position decoder 116. If the gear 300 is then rotated 360° back in anti-clock wise direction, the MT sensor 102 will measure only 2 full turns, and the measured linear position of the rack 302 will be adjusted accordingly since it is known how far the rack 302 will travel per revolution of the gear 300.
This arrangement provides a simple and accurate way of measuring the linear position of the rack 302 without the need for a linear sensing system being installed on the rack itself. Furthermore, by placing a single sensor package 308 containing both the MT sensor and the ST sensor in the same position, no calibration is required to align the readings of the two sensors since both sensors are measuring the same rotating magnetic field.
The rotating shaft 304 driving the gear 300 may be rotated using any suitable means, for example, using a motor 400, as shown in
The arrangement described above may also be supplemented with a second magnetic sensing device, as illustrated by
In this example, the magnet 406 is mounted on the end of a first rotating shaft 604A being driven by a motor 601, although it will be appreciated that any suitable drive means may be used, which in turn drives a first toothed gear 600A. The teeth of the first gear 600A are arranged to cooperate with the teeth of a second toothed gear 600B, which may also be mounted on a second shaft 604B for further structural support. It will also be appreciated that the magnet 606 and magnetic sensing device 608 could alternatively be arranged on the second shaft 604B, such that it rotates with the second gear 600B. The second gear 600B is then arranged to cooperate with the teeth of a toothed rack 602 so as to cause linear movement thereof. As the shaft 604A rotates, the first gear 600A rotates and causes a corresponding rotation of the second gear 600B in the opposite direction, which in turn causes the rack 602 to translate a corresponding distance in the linear direction, as described above with reference to the example of
As before, a magnetic sensing device 608 is located in the vicinity of the magnet 606 to thereby measure the magnetic field generated by the magnet 606 as the shaft 604A rotates. Based on the rotating magnetic field, the magnetic sensing device 608 measures the rotating magnetic field generated by the magnet 406 to measure the number of turns and absolute angular position of the first and second gears 600A, 600B, which can then be translated to a linear position of the rack 602, as described above.
As before, a single pole pair magnet 906 is mounted on the end of the rotating shaft 904 such that a rotating magnetic field is produced. A magnetic sensing device 908, which may be the magnetic sensing device 1 described with reference to
As described previously, the nut 902 is moved linearly as the leadscrew 900 rotates in one direction or the other. The magnetic sensing device 908 measures the rotating magnetic field generated by the magnet 906 to measure the amount by which the leadscrew 900 has rotated in either direction, by counting the number of turns made and the absolute angular position within each turn, or preferably, within each half turn, which is then used to determine the linear position of the nut 902. For example, the leadscrew 900 may be turned 2 full turns in a clockwise direction, as measured by the MT sensor 102, and a further 15°, as measured by the ST sensor 104. Based on these measurements and the proportional relationship between the respective movements of the leadscrew 900 and the nut 902, it may be determined, for example, by the position decoder 116, that the nut 902 has travelled 20 mm from left to right.
As described previously, this provides a simple and highly accurate way of measuring the linear position of the nut 902 without the need for a linear sensing system being installed on the nut itself. Furthermore, by placing a single sensor package 908 containing both the MT sensor and the ST sensor in the same position, no calibration is required to align the readings of the two sensors since both sensors are measuring the same rotating magnetic field.
As shown by way of example in
The arrangement described above with reference to
In this example, the magnet 1306 is mounted on the end of a first toothed gear 1310A. The teeth of the first gear 1310A are arranged to cooperate with the teeth of a second toothed gear 1310B, which is mounted on the shaft 1304 of the leadscrew 1300, such that the first toothed gear 1310A, the second toothed gear 1310B and the leadscrew 1300 all rotate together. It will be appreciated that the first toothed gear 1310A may be driven by some other means, such the rotation of the first toothed gear 1310A drives the rotation of the second toothed gear 1310B and the leadscrew 1300. Alternatively, the shaft 1304 of the leadscrew 1300 may be driven by some other means such as a motor, such that the rotation of the leadscrew 1300 drives the rotation of the first and second gears 1310A, 1310B.
As before, a magnetic sensing device 1308 is located in the vicinity of the magnet 1306 to thereby measure the magnetic field generated by the magnet 1306 as the first toothed gear 1310A rotates. Based on the rotating magnetic field, the magnetic sensing device 1308 measures the rotating magnetic field generated by the magnet 1306 to measure the number of turns and absolute angular position of the first and second gears 1300A, 1300B, and the leadscrew 1300, which can then be translated to a linear position of the nut 902, as described above.
It will be appreciated that the method and system for measuring linear position described herein may be applied to a number of different applications in which a component is driven in a linear direction by a rotational mechanism, including but not limited to, a clutch actuator, transmission actuators, seat position/rotation, electric sliding doors, sun roofs, electric sliding windows, tilt actuators, active suspension fork lift steering (tilt, position, extension), window blinds, window shutters, printers, elevators, machining equipment (a lathe machine, milling, wire cutting), a 3D printer, and dispensing/injection equipment.
The use of magnetic sensing device and magnet arrangement has significant advantages over the existing linear measurement systems currently used in such applications, in that it provides a significantly smaller, less complex and cheaper system. Furthermore, the magnetic sensor does not require power in order to measure the number of turns and angular position, and can therefore continue to output measurements if power is lost elsewhere.
Various modifications, whether by way of addition, deletion and/or substitution, may be made to all of the above described embodiments to provide further embodiments, any and/or all of which are intended to be encompassed by the appended claims
For example, in any of the arrangements described above, a shield in the form of cap or the like made from ferromagnetic material may be placed around the magnet and magnetic sensing device to protect it from stray magnetic fields that may disturb the turn count and angle measurements.
In other examples, the system may be provided with an electromagnet that initializes the magnetic sensing device when the rotatable mechanism and driven element are at a starting position, for example, when the driven element is at one of its end positions or in its middle position. Preferably, the electromagnet will be located in proximity to the MT sensor to align the magnetisation of all of the magnetoresistive elements in one direction. That is to say, when the driven element is at its starting position, the electromagnet may initialize the magnetic sensor such that this position corresponds to a zero turn count reading by the MT sensor, and a zero degree angle reading by ST sensor. This then provides the starting point from which the turn count and angle are measured as the rotatable mechanism rotates to drive the element linearly.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/077713 | 10/2/2020 | WO |
